Replacement lintels

I have three window lintels to replace as the builders say because the existing support is angle
Iron bearing down on the pvc window frame 1x 2600 lintels 1x 2000 lintels and 1x1200 lintels plus scaffolding to first floor what would be a fair estimate thanks

I have seen the angle iron which is very rusty but I will look into it further in the meantime the lintels are about £150 each which have an overhang of 100mm either side so apart from scaffold, he says he can replace bricks the cost will be APPROX £600 for largest window and slightly less for the smaller ones does this sound about right

On a slightly different note does the lintels come with a guarantee thank Allan